Decoupling of actuators for positioning an object

Abstract

The invention provides an apparatus and a method for positioning an object coupled to a first support structure and a second support structure. A first actuator drives the first support structure along a first axis and a second actuator drives the first support structure along a second axis orthogonal to the first axis. A third actuator comprising a forcer and a stator is provided for driving the second support structure that is guided for movement relative to the first support structure along a third axis orthogonal to the first and second axes. The forcer is coupled to the second support structure and is movable with respect to the stator, and the stator is relatively stationary and decoupled from the second support structure.

Description

FIELD OF THE INVENTION [0001] The invention relates to the use of motorized actuators cooperating to drive and position an object, such as an end effector attached to an XYZ linear motion table, in different orthogonal directions. BACKGROUND AND PRIOR ART [0002] Linear motion tables that are movable in orthogonal X, Y and Z axes (also called XYZ linear motion tables) have gained popularity in the machine tool and semiconductor industries due to the complexity of motion combinations demanded for the applications used in such industries. One common application is the use of actuators for driving an object, for example a semiconductor bond head which is attached to a support structure such as a table or platform. By controlling the position of the platform or table, the bond head may be positioned accordingly. [0003] The simplest configuration for an XYZ linear motion system is the with three overlying linear motion tables, the motion of each table being controlled by an actuator coupl...

AI Technical Summary

Benefits of technology

"The invention provides a way to move an object in different directions using multiple actuators. One of the actuators is separate from the others, which helps to avoid some of the problems of previous designs. The first actuator moves the object along one axis, the second actuator moves it along another axis, and the third actuator moves it along a third axis. The first and second actuators are separate from the third actuator, and the third actuator is a forcer and stator that work together to move the object. This design allows for more precise and accurate positioning of the object."

Problems solved by technology

However the size as well as the weight of the actuator supported by another table and driven by another actuator are obstacles in obtaining high speed motion and position with extreme accuracy.

When the loads on the motion axes are increased, various problems such as vibration of the structure arise so that complexity of the system may need to be increased to try to contain the problems.

Failure to decouple the various motion axes means that at least one table and actuator is required to take up the dummy load of another table and actuator.

The additional load may well be insignificant if the actuators consist of solenoid, pneumatic cylinder motor or the like which have relatively smaller weights.

However, with demand increasing for higher positioning accuracy and faster acceleration, the use of a linear motor having a heavy stator weight would cause greater concern.

However, the wearing out of the auxiliary coupler 47 as well as the surface 48 after prolonged use of the system may adversely affect both the leveling and positional accuracy of the XYZ table.

However the wearing out of the above contacted parts is inevitable due to the friction produced between surfaces.

Furthermore, the force from the anti-backlash or tension spring which keep the mating surfaces in permanent contact should be great enough, otherwise the table will oscillate due to slow response to actuation during fast acceleration.

This causes an increase in the frictional forces which will expedite the wearing of the contacted parts.

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